My brother has a motherboard with several PCI-E x1 slots. He currently has a 4850 hooked up that he uses exclusively. If I hook up one or more GPUs on the same board and use them at full load with Bitcoin, will it affect his video performance on his 4850 in any way? This is assuming I can pick and choose what video devices I want Bitcoin to generate on. Can I?

In addition, will a quality 500W dual-rail OCZ power supply be able to support a dual-core CPU (E8200), a 4850 and a 5770?

Thank you.

I am very new to the Bitcoin community so I can't comment on your question but his options for PCI-E x1 gpu's are very limited and low preforming http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=100007709%20600007854&IsNodeId=1&name=PCI%20Express%20x1

True, but the connector must be the right size - and cards used for mining on the market use a physical x16 connector.

If you feel safe hacking the slot and having little retention for something with more weight than what is typically in an x1 slot, go for it